Seismic Interpretation of Visean-Bashkirian Carbonate Platforms in the Pricaspian Basin

We present the results of the seismic interpretation of high quality, long–offset 2D seismic surveys which have allowed the construction of a palaeogeographical and structural framework of the Caspian Sea sector of the Pricaspian Basin. This sector of the Pricaspian Basin is characterised by a series of carbonate platforms and intervening shale-dominated troughs formed during the Middle Devonian-Early Permian. These structures may be entirely isolated or faulted, with flat roof-tops and the intervening younger strata onlap the slopes around the structures. This interpretation, suggests the following sequential depositional and structural model for the Late Proterozoic-Palaeozoic which then has profound implications for subsequent deposition in the basin: (1) subsidence during an active rifting phase in Riphean times; (2) Devonian rifting ; (3) significant subsidence during the Late Devonian- Middle Carboniferous, with carbonate build-up on the shallow margins and shale deposition in the deep water; (4) increased subsidence due to the collision of the Russian Craton with the Kazakh continent during the Late Carboniferous;(5) salt deposition in the isolated incipient Caspian Sea (6) salt deformation as syn-orogenic sediments were deposited during the Late Permian and onwards